针对直升机特有的涡环飞行状态，根据直升机空气动力学理论，分析了直升机涡环状态飞行事故的现象及成因。

To investigate helicopter vortex-ring state, the phenomenon and reason of helicopter vortex-ring state flight accident is analyzed from the view of helicopter aerodynamics.

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综合气动性能最佳的高速列车头部形状，可有效地降低空气动力学现象对列车运行和周围环境的影响。

The nose shapes of high-speed trains with optimal synthetic aerodynamic performance can efficiently reduce the influence of the aerodynamic phenomena on the train operation and the environment.

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